Ebola: an unwanted guest

The ebola epidemic that is sweeping across countries in West Africa has so far caused more than 1700 cases and almost 1000 deaths and is one of the most deadly outbreaks to have occurred.

Quite possibly thousands of people have been exposed to the disease and as many have fled and cannot be found, we may never know the full impact of this deadly outbreak. In parts of Liberia fear rules and panic is rife.

Ebola victims are often left on the roadside abandoned by fearful relatives. Throughout affected areas people remain highly suspicious of hospitals and isolation wards. In parts of Liberia troops have been deployed to quarantine affected communities.

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Ebola is a viral disease that is probably permanently maintained among bat or ape and monkey populations. Since the first outbreak in 1976, ebola has probably affected thousands of people and killed between 40 and 80 percent of those affected. The virus is constantly circulating among its animal hosts, most probably bats in parts of West and Central Africa.

Every so often it spreads to humans, often when people intrude upon and disturb natural reservoirs of the disease, or when they eat raw or undercooked meat from an infected bat, ape or monkey. For humans the disease is relatively difficult to catch, most commonly resulting from direct contact with the blood or bodily fluids of an infected person or animal.

The symptoms include fever, headaches, vomiting and diarrhea as well as internal and external bleeding. Ebola is not spread by airborne droplets but by the exchange of body fluids. In many ways this differentiates the disease from other infectious threats which spread easily among humans.

So are we at risk particularly given that at least three cases have turned up in the USA albeit two of which were returned under care from West Africa? Currently there are also some suspected cases in Europe but they remain to be confirmed. Is there any chance of ebola reaching Australia and if it did what might be the result?

Well, in August Bio.Dispora provided some data on the final destination of airline passengers leaving Guinea, Liberia and Sierra Leone. More than 1,000 passengers were destined for the Western Pacific, including Australia, while more than 10,000 headed for Europe.

As we found out during the SARS and Avian Flu epidemics sheer distance and isolation from the rest of the world is no defense. Infectious disease recognizes no borders and in a modern age of substantial human mobility, such diseases move around the world at will. Nowhere is safe and although we are frequently told that Australia has one of the best border surveillance and protection systems in the world and that Customs and Border Protection Officers would be on the watch for sick passengers arriving in Australia, how confident can we be that this would offer us protection.

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In particular, given that the symptoms associated with ebola can take up to 21 days to reveal themselves, it would be very easy for someone who had been exposed to the disease to enter Australia, having perhaps only left West Africa 20 hours before and exhibiting no signs of illness. Possibly such a person might also simply put on their arrival card that they had spent some time in Africa or Southern Africa rather than West Africa.

It is therefore highly unlikely that Australian border controls would be able to identify and stop the arrival of an infected person into Australia. And how many people on that flight back to Australia might have been inadvertently exposed to the infection either by using the same aircraft toilet, handling a plate, glass or magazine that the person in question may have coughed over, or perhaps even being exposed when the person in question threw up in the Arrivals toilet.

Currently there are of the order of 50 Australians travelling around West Africa as well as several hundred in the broader region. While the risk of infection to such people is low, vigilance remains critical. But if an unidentified case did reach Australia what might be the result? Possibly we might see the emergence of one or more localized clusters of the disease and given that suspected cases would be quickly quarantined these would soon die out. Even so it is quite possible that a few deaths might also occur.